Public utilities have recently been developing methods and systems to support computerized power management. Much of the impetus for such automated power management comes as a result of the massive power failure that occurred in the fall of 1966. At that time, it became evident that some kind of centralized grid control would be needed to provide an overall fail safe method for preventing similar occurrences in the future.
A part of such an overall electric-power management system will entail the use of an automatic, electric-meter readout device which will adapt to existing home and industrial meters and eliminate the need for individual readout of meters by utility employees or the like.
U.S. Pat. No. 3,733,586 discloses a special communications system which can be used to feed data directly into power lines. Thus, the same wires that connect power into a home or other utilization zone can be used to transmit communications signals. This system opened the door to the possibility of automatic meter readout without the necessity of stringing extra wires to each subscriber for that purpose.
However, a present obstacle exists which, thus far, has prevented widespread use of automatic metering systems. This obstacle is the lack of an inexpensive device which can be adapted to the already installed house meters and which can transmit signals over power lines on command. Since the public utilities have many millions of dollars tied up in house and industrial meters, which are designed to last from twenty-five to forty years, it is understandable that the expense of replacing the present meters, with new ones having the desired automated readout capability, would be financially undesirable. Thus, a device which can be readily adapted to the various meter types, of which there are many, must be inexpensive, easily installable, and trouble-free for the life of the meter.
A number of automatic readout adapters have been developed and these are of two general categories of design. A contact method, which is inexpensive, has been ruled out because it causes excessive drag on the meter mechanism, thereby invalidating the calibration. The second category involves the electro-optical readout of meter dials. The latter method is desirable because it eliminates physical contact with the metering dials. However, to date, all such techniques have proven very expensive.